Category: Linked Lists & Stacks

Linked lists and stacks are the structures where small pointer mistakes turn into infinite loops or lost nodes, and this category covers both. The linked list guide works through the classic problems in Python: reversing a list, detecting a cycle, finding the middle, merging two sorted lists and removing the nth node from the end, using techniques such as fast and slow pointers and dummy nodes. The monotonic stack guide shows a different tool, a stack that keeps its elements in order so that questions like next greater element, daily temperatures and largest rectangle in a histogram can be answered in a single pass. Together they train two habits interviewers look for: drawing the structure before you code, and checking the empty and single-element cases before you submit.